JPH07194137A - Power converter - Google Patents

Abstract

PURPOSE:To prevent the breakdown of controlled rectifier elements by providing voltage limiter means in inversely parallel with the controlled rectifier elements, detecting means which detect electric currents when the voltage limiter means operate, and protective means which are operated by the detected signals of the detector means. CONSTITUTION:First to fourth controlled rectifier elements 4-7 are connected in series between both terminals of capacitors 2a and 2b which are connected to a DC side 1 and have a neutral point 3 and first and second clamp diodes 16 and 17 are respectively connected between the connecting point between the first and second controlled rectifier elements 4 and 5 and the neutral point 3 and between the connecting point between the third and fourth controlled rectifier elements 6 and 7 and the neutral point 3. In such a power converter, voltage limiter means 4b-15b which are connected in inversely parallel with controlled rectifier elements 4-15, detecting means 26-37 which detect electric currents when the means 4b-15b operate, and protective means which stop the operations of the elements 4-15 by using the detected signals of the means 26-37 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter using a semiconductor element.

[0002]

2. Description of the Related Art FIG. 9 is a circuit diagram showing a configuration of a neutral point clamp type power conversion device adopted as a conventional electric vehicle control device. A structure similar to this is available from the Electric Vehicle Study Group “Science of Electric Vehicles” June 1993 Vol. 46th 21st
There is FIG. 4 on pages 27-27. In the figure, 1 is a DC power supply, 2a and 2b are connected to the DC power supply 1, and capacitors of the same rating for dividing the DC voltage are used. 3 is capacitors 2a and 2
It is a neutral point derived from the interconnection point with b.

4 to 15 are IGBTs as control rectifying elements
A three-phase bridge connection with an element. Reference numerals 4a to 15a are diodes connected in antiparallel to the IGBT elements 4 to 15, respectively. 16 is a clamp diode (also referred to as a freewheeled diode) connected between the neutral point 3 and the connection point of the IGBT elements 4 and 5, and 17 to 21 are the neutral point 3 and each IGBT similarly to the clamp diode 16. Elements 6 to 1
5 is a clamp diode connected to each connection point 5. The IGBT elements 4 to 15 and the diodes 4a to
15a, clamp diodes 16 to 21 with 3-level type 3
The phase inverter 22 is configured.

Reference numeral 23 is an induction motor for driving an electric vehicle connected to the AC output side of the three-level inverter 22, V is a voltage command, f _M is a detected rotation frequency of the induction motor 23, and G11 to G11.
G22 is a gate signal for controlling ignition / extinction of each of the IGBT elements 4 to 15, and 24 is a PW for calculating conduction / non-conduction of each of the IGBT elements which is the basis of the gate signals G11 to G22.
The M operation circuits S11G to S22G are operation values which are the basis of the gate signals G11 to G22 to be sent to the IGBT elements 4 to 15 for the three phases (U, V, W phases) of the three-level inverter 22, respectively. 25 receives the voltage command V and the detected rotation frequency f _M of the induction motor 23, and outputs the gate signals G11 to G11.
22 is a control circuit for generating 22.

Next, the operation will be described. When a power running start command is output from a driver's cab (not shown), the DC overhead wire voltage E
d is supplied to the three-level inverter 22 via the DC power supply 1 and the capacitors 2a and 2b. The control circuit 25 creates gate signals G11 to G22 from the voltage command V and the rotation frequency f _M of the induction motor 23, and uses them to generate the IGBT elements 4
To 15 for on / off control to generate a three-phase AC voltage having a variable voltage and variable frequency from the three-level inverter 22, and the induction motor 23 is driven at a variable speed by receiving the AC output.

Next, the PWM (pulse width modulation) operation will be described. FIG. 10 is a time chart showing an operation example of the PWM arithmetic circuit 24. In the figure, M is a sine-waveform command signal wave, which changes according to the voltage command V to be output as the three-level inverter 22. C is a triangular carrier wave, and its frequency determines the number of times of conduction (non-conduction) of one cycle. In the example in the figure, the number of times of conduction in one cycle is 4, but the number of times of conduction is changed according to the vehicle speed, and as the speed changes from low speed to high speed, for example, 28 → 16 → 10 →
Change from 4 to 2 to once.

S11G to S14G of FIG. 10 are IGBT elements 4 to 4 of U phase for one phase of the three-level inverter 22, respectively.
7 is a calculated value which is a basis of the gate signals G11 to G14 to be sent to No. Here, the basic operation of the three-level inverter will be described. FIG. 11 is an explanatory diagram showing the relationship between the switching states of the IGBT elements 4 to 7 for one phase and the output phase voltage, and is + for each of the switching states of A, B, and C.
Phase voltages of Ed / 2, 0, -Ed / 2 are output. Figure 1
In the first half of one cycle shown in 0, among the switching states,
B → A → B, and in the latter half, B → C → B.

Therefore, the waveforms of the calculated values S11G to S14G are as follows. That is, S11G in the first half cycle is conductive (H level) when the command signal wave M ≧ carrier C and is non-conductive (L level) in the remaining time period. S12G is always conductive (H level). S13G is non-conducting (L level) when the command signal wave M ≧ modulating wave C, and conducting (H level) in the remaining time zone.
level). S14G is always non-conductive (L level).

In the latter half period, S11G is always non-conductive (L level). S12G is non-conductive (L level) when the command signal wave M ≧ modulated wave C, and is conductive (H level) in the remaining time zone. S13G is always conductive (H level). S14G is conductive (H level) when the command signal wave ≧ modulation wave C, and is non-conductive (L level) in the remaining time zone.

Since the respective calculated values S11G to S14G are created as described above, for example, when the swing width of the command signal wave M increases, the conduction time zones of the IGBT elements 4 and 7 increase accordingly. Therefore, the time zones of the switching states A and C increase with respect to the switching state B, and as a result, the output voltage increases. Vuo and Vvo in FIG. 10 are I
U-phase and V-phase output waveforms obtained when the GBT element is on / off controlled by the above calculated value S11G and the like,
Vuv is a line voltage waveform obtained between U and V.

The diodes 16 to 21 clamp the main circuit voltage applied to the IGBT elements 4 to 15 in the capacitors 2a and 2b in the process of the modulation operation, so that the DC voltage Ed is obtained.
Since the number can be reduced to half, the inverter circuit can be configured using the controlled rectifying element having a low withstand voltage.

[0012]

Since the conventional power converter is configured as described above, when an abnormality occurs in the ignition / extinguishing order of the controlled rectifying element due to a failure of the control circuit or the like, For example, when the second controlled rectifying element 5 reaches an arc extinguishing operation while the first controlled rectifying element 4 and the second controlled rectifying element 5 are conducting, the first clamp diode 16 changes the voltage of the capacitor 2a. Reverse bias is applied, the neutral point clamp function does not work, and the entire DC voltage is applied to the second controlled rectifying element 5. Therefore, there is a problem that an abnormal voltage is applied to the second controlled rectifying element 5 and the breakdown voltage is destroyed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a power conversion device capable of preventing breakdown of a controlled rectifying element by withstand voltage.

[0014]

In the power converter according to the present invention, voltage limiting means is provided in antiparallel with the control rectifying element, and detecting means for detecting a current when the voltage limiting means operates, and this detecting means. The protection means is operated by the detection signal of.

Further, the control rectifying element is provided with voltage limiting means in anti-parallel, the detecting means for detecting the voltage when the voltage limiting means operates, and the protection means operated by the detection signal of the detecting means. Is.

Further, a diode is provided in antiparallel with the controlled rectifying element, and a first anode igniting means connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage, and control of the controlled rectifying element. Second anode firing means connected between the terminal and the cathode and conducting at a predetermined voltage, detection means for detecting the voltage of the second anode firing means, and protection means operated by the detection signal of the detection means. It is equipped with.

Further, a diode is provided in antiparallel to the controlled rectifying element, and a first anode igniting means connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage, and control of the controlled rectifying element. The second anode ignition means connected between the terminal and the cathode and conducting at a predetermined voltage, the detection means for detecting the current when the first anode ignition means operates, and the detection signal of the detection means It is provided with a protection means that operates.

Then, a diode is provided in antiparallel to the controlled rectifying element, and first anode igniting means for conducting at a predetermined voltage between the anode of the controlled rectifying element and the control terminal, and the control terminal of the controlled rectifying element. A second anode ignition means that conducts at a predetermined second voltage connected to the cathode, a detection means that detects the voltage between the anode and the cathode of the controlled rectifying element, and a detection signal of the detection means. It is provided with a protection means that operates.

[0019]

In the power converter according to the present invention, the voltage limiting means is provided in antiparallel with the control rectifying element so that the voltage limiting means maintains the avalanche voltage during an abnormal state in which the control rectifying element is extinguished during the ignition operation. Flow in the opposite direction. The reverse current is detected by the detection means, the protection means is operated by the detection signal of the detection means, and the voltage divided by the clamp diode is applied to the control rectifying element.

Further, the voltage limiting means is provided in antiparallel to the control rectifying element, and the voltage of the control rectifying element rises at the abnormal time of extinguishing during the ignition operation of the control rectifying element, and the voltage limiting means reaches the avalanche voltage. . This voltage is detected by the detection means, the protection means is operated by the detection signal of this detection means, and the voltage divided by the clamp diode is applied to the control rectifying element.

Further, a diode is provided in antiparallel to the controlled rectifying element, and first anode ignition means connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage, and control of the controlled rectifying element. Second anode igniting means connected between the terminal and the cathode and conducting at a predetermined voltage, detecting means for detecting the voltage of the second anode igniting means, and protection operated by a detection signal of the detecting means. Since the control rectifying element is equipped with means, the voltage of the control rectifying element rises in the abnormal state of extinguishing during the ignition operation of the control rectifying element, and when the first anode igniting means reaches the constant voltage operating voltage, the current flows in the reverse direction. And the control rectifying element is ignited by the anode. The detection means detects the voltage rise of the second anode ignition means due to the voltage rise of the control rectifying element, and the protection means is operated by the detection signal generated from this detection means to control the voltage divided by the clamp diode. It affects the rectifying element.

Further, a diode is provided in antiparallel to the controlled rectifying element, and a first anode ignition means connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage, and control of the controlled rectifying element. A second anode firing means connected between the terminal and the cathode and conducting at a predetermined voltage, a detection means for detecting a current when the first anode firing means operates, and a detection signal of this detection means. Since the protective means for operating by the control means is provided, the detecting means detects the current flowing when the anode igniting means operates at the abnormal time of extinguishing during the ignition operation of the control rectifying element. The protective means is activated, and the voltage divided by the clamp diode is applied to the controlled rectifying element.

A diode is provided in antiparallel to the controlled rectifying element, and a first anode ignition means connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage, and control of the controlled rectifying element. Second anode ignition means connected between the terminal and the cathode and conducting at a predetermined voltage, detection means for detecting the voltage between the anode and cathode of the controlled rectifying element, and operated by the detection signal of the detection means Since the protective means is provided, the detecting means detects that the voltage of the control rectifying element has risen in the abnormal state of extinguishing during the ignition operation of the controlling rectifying element, and operates the protective means by the detection signal of this detecting means. Then, the voltage divided by the clamp diode is applied to the controlled rectifying element.

[0024]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a neutral point clamp type power conversion device. In the figure, 1 to 25 are the same as conventional ones. 4b to 15b are avalanche diodes as voltage limiting means connected in antiparallel to the respective IGBT elements, and 26 to 37 are avalanche diodes 4b to 1
5b is a current detector as a detecting means for detecting the current flowing through 5b. The IGBT elements 4 to 15 and the diode 4
b-15b, clamp diodes 16-21, and current detectors 26-37 form a three-level three-phase inverter 38. The current detectors 26 to 37 are connected to protection means (not shown) in the control circuit 25.

Next, the operation will be described. FIG. 2 is an explanatory diagram showing the operation when the voltage limiting means of FIG. 1 operates.
1 and 2, a case will be described in which the IGBT element 5 reaches the arc extinguishing operation due to a mistake in the modulation logic or the like while the IGBT elements 4 and 5 are conducting. I at t ₁
Voltage of GBT element 5 rises and reaches the avalanche voltage of the avalanche diode 5b in t _2, avalanche diode 5b is diverted in a reverse direction current while maintaining the avalanche voltage from the cathode to the anode. The reverse current is detected by the current detector 27, and the operation of the avalanche diode 5b is detected. A protection means (not shown) in the control circuit 25 makes the IGBT element 4 non-conductive by the detection signal of the current detector 27. When the IGBT element 4 becomes non-conductive at t ₃ , the clamp diode 16 operates and the divided voltage is applied to the IGBT element 5, and the avalanche diode 5b shifts from the avalanche state to the normal voltage sharing state.

Example 2. FIG. 3 is a circuit diagram showing the configuration of a neutral point clamp type power converter according to another embodiment. In the figure, 1 to 25 are the same as conventional ones. 39 ~
Reference numeral 50 denotes a voltage detector as detection means connected in parallel to each of the avalanche diodes 4b to 15b. The voltage detector 50 detects the avalanche voltage of each of the avalanche diodes 4b to 15b and outputs the detection signal to the protection means (not shown) in the control circuit 25. Have been sent to. The IGBT elements 4 to 15, the avalanche diodes 4b to 15b, the clamp diodes 16 to 21, and the voltage detectors 39 to 50 constitute a three-level type three-phase inverter 51. Even if the avalanche voltage of the avalanche diode 5b is detected as shown in FIG. 3, an error in the arc extinguishing operation can be detected as in the first embodiment.

Example 3. Another embodiment of the present invention will be described with reference to FIG. In the figure, 1 to 25 are the same as conventional ones. Reference numerals 52 to 63 are constant voltage diodes connected in antiparallel between the anodes of the respective IGBT elements 4 to 15 and control terminals, 64 to 75 are connected to the respective constant voltage diodes 52 to 63, and the other is the respective IGBT elements 4 Limiting resistors connected to the control terminals of ˜15. In addition, each constant voltage diode 5
2 to 63 and the respective resistors 64 to 75, the respective anode ignition means 76 to 87 are formed.

88 to 99 are constant voltage diodes connected between the control terminals and the cathodes of the IGBT elements 4 to 15 and 1
Reference numerals 00 to 111 denote voltage detectors as detecting means connected in parallel to the constant voltage diodes 88 to 99. The voltage detectors 100 to 111 are connected to a protection means (not shown) in the control circuit 25. The IGBTs 4 to 15, the diodes 4a to 15a, the clamp diodes 16 to 21,
Anode firing means 76-87, constant voltage diodes 88-9
9. The voltage detectors 100 to 111 form a three-level three-phase inverter 112.

Next, the operation will be described. While the IGBT elements 4 and 5 are conducting, the I
When the IGBT element 5 reaches the arc extinguishing operation, the IGBT element 5
When the voltage rises and reaches the constant voltage operating voltage of the constant voltage diode 53, the constant voltage diode 53 causes a current to flow in the reverse direction. This current is limited by the limiting resistor 65, and a voltage or current is supplied to the control terminal of the IGBT element 5 to ignite the IGBT element 5.

If the IGBT element has once ignited and does not have a mechanism (latch-up mechanism) for maintaining this ignition state, I
The GBT element 5 is almost extinguished. IGBT when extinguished
Although the current or voltage supplied to the element 5 is amplified, the voltage determined by the constant voltage diode 53 and the constant voltage diode 89 is maintained so that the voltage rise applied to the control terminal of the IGBT element 5 becomes equal to or less than the specified value. keep.

When the IGBT element 5 reaches the arc extinguishing operation,
The voltage detector 101 detects the voltage rise of the constant voltage diode 89 caused by the voltage rise of the IGBT element 5. In response to the detection signal of the voltage detector 101, a protection means (not shown) in the control circuit 25 makes the IGBT element 4 non-conductive. I
When the GBT element 4 becomes non-conductive, the clamp diode 1
The voltage divided by the operation of 6 is applied to the IGBT element 5 to shift to a normal voltage sharing state.

Example 4. FIG. 5 is a circuit diagram showing the configuration of a power conversion device according to another embodiment. In the figure, 1 to 99 are the same as in the third embodiment. Reference numerals 113 to 124 denote current detectors provided between the anodes of the IGBT elements 4 to 15 and the control terminals. The IGBT elements 4 to 15, the diodes 4a to 15a, the clamp diodes 16 to 21, the constant voltage diodes 52 to 63, the limiting resistors 64 to 75, the constant voltage diodes 88 to 99, and the current detectors 113 to 124 are three-level inverters. 125 is configured. As shown in FIG. 5, current detectors 113 to 124 for detecting the currents flowing through the anode ignition means 76 to 87 may be provided, and an error in the arc extinguishing operation can be detected as in the first embodiment.

Example 5. FIG. 6 is a circuit diagram showing the configuration of the neutral point clamp type power conversion device according to the fifth embodiment. In the figure, 1 to 99 are the same as in the third embodiment. 126-1
Reference numeral 37 is a voltage detector provided between the anode and the cathode of each of the IGBT elements 4 to 15. In addition, the IGBT elements 4-1
5, diodes 4a to 15a, constant voltage diode 52 to
63, limiting resistors 64 to 75, constant voltage diodes 88 to 9
9. Three-level inverter 1 with voltage detectors 126-137
38.

In the third embodiment, the voltage detector for detecting the voltage of the constant voltage diode 89 is provided in order to detect the voltage rise when the IGBT element 5 is abnormal, but as shown in FIG.
A voltage detector 127 that detects the voltage between the anode and the cathode of the element 5 may be used, and the same effect as that of the third embodiment can be obtained.

Example 6. In the above embodiment, a three-phase inverter has been described as an example, but if the configuration of one phase is of the neutral point clamp type, it can be applied to both single phase and multi-phase.

Example 7. 7 and 8 show a converter, which is also applicable to the first to sixth embodiments. In addition,
The constant voltage diode of each anode firing means need not be an avalanche type, as long as it conducts at a predetermined voltage.

[0037]

As described above, according to the present invention, in the power converter, the voltage limiting means is provided in antiparallel with the controlled rectifying element, and the detecting means for detecting the current when the voltage limiting means operates, Since the protection means that operates by the detection signal of the detection means is provided, the voltage limiting means allows the current to flow in the reverse direction while maintaining the avalanche voltage at the time of an abnormality that the control rectifying element is extinguished during the ignition operation. Is detected by the detection means, the protection means is operated by the detection signal output from the detection means, and the voltage divided by the clamp diode is applied to the control rectifying element, so that the breakdown voltage of the control rectifying element can be prevented from being destroyed.

Further, the control rectifying element is provided with the voltage limiting means in anti-parallel, the detecting means for detecting the voltage when the voltage limiting means operates, and the protection means for operating by the detection signal of the detecting means. , The voltage of the control rectifying element rises at the time of an abnormal state of extinguishing during the ignition operation of the control rectifying element,
The voltage limiting means reaches the avalanche voltage. This voltage is detected by the detection means, the protection means is operated by the detection signal output from the detection means, and the voltage divided by the clamp diode is applied to the control rectifying element, so that the breakdown voltage of the control rectifying element can be prevented.

Further, a diode is provided in antiparallel to the controlled rectifying element, and a first anode igniting means connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage, and control of the controlled rectifying element. Second anode igniting means connected between the terminal and the cathode and conducting at a predetermined voltage, detecting means for detecting the voltage of the second anode igniting means, and protection operated by a detection signal of the detecting means. Since the control rectifying element is equipped with means, the voltage of the control rectifying element rises in the abnormal state of extinguishing during the ignition operation of the control rectifying element, and when the first anode igniting means reaches the constant voltage operating voltage, the current flows in the reverse direction. And the control rectifying element is ignited by the anode. The detection means detects the voltage rise of the second anode ignition means due to the voltage rise of the control rectifying element, and the protection means is operated by the detection signal generated from this detection means to control the voltage divided by the clamp diode. It is possible to prevent breakdown of the control rectifying element due to the rectifying element.

Further, a diode is provided in antiparallel to the controlled rectifying element, and a first anode igniting means connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage, and control of the controlled rectifying element. A second anode ignition means connected between the terminal and the cathode and conducting at a predetermined voltage, a detection means for detecting a current when the anode ignition means operates, and a detection signal of the detection means. Since the protective means is provided, the detecting means detects the current flowing when the anode igniting means operates at the abnormal time of extinguishing the arc while the control rectifying element is igniting operation, and the protecting signal is generated by the detecting signal from the detecting means. Is operated, the voltage divided by the clamp diode is applied to the control rectifying element, and the breakdown voltage of the control rectifying element can be prevented.

A diode is provided in antiparallel to the controlled rectifying element, and a first anode ignition means connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage, and control of the controlled rectifying element. Second anode ignition means connected between the terminal and the cathode and conducting at a predetermined voltage, detection means for detecting the voltage between the anode and cathode of the control rectifying element, and operated by the detection signal of the detection means Since the protective rectifying element is provided, the voltage of the control rectifying element rises at the abnormal time of extinguishing during the ignition operation of the control rectifying element, and the detecting means detects this voltage,
The protection means is operated by the detection signal generated by the detection means, and the voltage divided by the clamp diode is applied to the control rectifying element, so that the breakdown voltage of the control rectifying element can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a neutral point clamp type power conversion device showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an operation when the voltage limiting means of FIG. 1 operates.

FIG. 3 is a circuit diagram showing a configuration of a neutral point clamp type power conversion device showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a neutral point clamp type power conversion device according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a neutral point clamp type power conversion device showing a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram showing a configuration of a neutral point clamp type power conversion device according to a fifth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a converter showing a seventh embodiment of the present invention.

FIG. 8 is a circuit diagram showing a converter according to a seventh embodiment of the present invention.

FIG. 9 is a circuit diagram showing a configuration of a neutral point clamp type power conversion device used as a conventional electric vehicle control device.

10 is a time chart showing an operation example of the PWM operation circuit used in FIG.

FIG. 11 is an explanatory diagram showing the relationship between the switching state of the IGBT element for one phase and the output phase voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2a, 2b Capacitor 4-15 Control rectification element 4b-15b Voltage limiting means 16-21 Clamp diode 26-37 Detection means 39-50 Detection means 76-87 Anode ignition means 88-99 Constant voltage diode (anode point Arc means) 100-111 Detection means 113-124 Detection means 126-137 Detection means

Claims (6)

[Claims] 1. A first controlled rectifying element to a fourth controlled rectifying element are connected in series between both terminals of a capacitor which is connected to a DC side and has a neutral point. Between the interconnection point with the second controlled rectifying element and the neutral point, and between the interconnection point with the third controlled rectifying element and the fourth controlled rectifying element and the neutral point. In the power converter to which the first and second clamp diodes are connected, voltage limiting means connected in antiparallel to each of the control rectifying elements, and detecting means for detecting a current when the voltage limiting means operates. And a protection means for stopping the operation of each of the controlled rectification elements by the detection signal of the detection means. 2. The power conversion device according to claim 1, wherein the detection means is a current detector that detects a current in the avalanche direction of the diode. 3. A first controlled rectifying element to a fourth controlled rectifying element are connected in series between both terminals of a capacitor which is connected to the DC side and has a neutral point. Between the interconnection point with the second controlled rectifying element and the neutral point, and between the interconnection point with the third controlled rectifying element and the fourth controlled rectifying element and the neutral point. In the power converter to which the first and second clamp diodes are connected, voltage limiting means connected in antiparallel to each of the control rectifying elements, and detecting means for detecting a voltage when the voltage limiting means operates. And a protection means for stopping the operation of each of the controlled rectification elements by the detection signal of the detection means. 4. When the ignition signal is applied to the control terminal by being connected in series between both terminals of the capacitor having a neutral point connected to the DC side, the ignition signal is applied between the anode and the cathode. Between the first controlled rectifying element and the fourth controlled rectifying element, which flow a corresponding current, and between the interconnection point of the first controlled rectifying element and the second controlled rectifying element and the neutral point. And a power converter in which first and second clamp diodes are connected between an interconnection point of the third controlled rectifying element and the fourth controlled rectifying element and the neutral point. A diode connected in anti-parallel between the anode and the cathode of the controlled rectifying element, and a first anode connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage. Between the ignition means and the control terminal of each of the control rectifying elements and the cathode A second anode igniting means connected at a predetermined voltage, a detecting means for detecting a voltage across the second anode igniting means, and a detection signal of the detecting means for detecting the control rectifying element. A power conversion device comprising: a protection unit that stops the operation. 5. The ignition signal is connected between the anode and the cathode when the ignition signal is applied to the control terminal by being connected in series between both terminals of the capacitor connected to the DC side and having a neutral point. Between the first controlled rectifying element and the fourth controlled rectifying element, which flow a corresponding current, and between the interconnection point of the first controlled rectifying element and the second controlled rectifying element and the neutral point. And a power converter in which first and second clamp diodes are connected between an interconnection point of the third controlled rectifying element and the fourth controlled rectifying element and the neutral point. A diode connected in anti-parallel between the anode and the cathode of the controlled rectifying element, and a first anode connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage. Between the ignition means and the control terminal of each of the control rectifying elements and the cathode A second anode igniting means which is connected to a predetermined voltage and which conducts, a detecting means for detecting a current when the first anode igniting means operates, and the control rectification based on a detection signal of the detecting means. A power conversion device comprising: a protection unit that stops the operation of the element. 6. The ignition signal is connected between the anode and the cathode when the ignition signal is applied to the control terminal by being connected in series between both terminals of the capacitor connected to the DC side and having a neutral point. Between the first controlled rectifying element and the fourth controlled rectifying element, which flow a corresponding current, and between the interconnection point of the first controlled rectifying element and the second controlled rectifying element and the neutral point. And a power converter in which first and second clamp diodes are connected between an interconnection point of the third controlled rectifying element and the fourth controlled rectifying element and the neutral point. A diode connected in anti-parallel between the anode and the cathode of the controlled rectifying element, and a first anode connected between the anode of the controlled rectifying element and the control terminal and conducting at a predetermined voltage. Between the ignition means and the control terminal of each of the control rectifying elements and the cathode A second anode igniting means which is connected with a predetermined voltage and which conducts, a detecting means for detecting a voltage between the anode and the cathode of the controlled rectifying element, and each of the control rectifications by a detection signal of the detecting means. A power conversion device comprising: a protection unit that stops the operation of the element.